Simulação do comportamento escória/aço durante o esgotamento da panela através de modelagem física

Abstract

Slag is present in the majority of the operations involved in steelmaking processes and plays a significant role in protecting steel from reoxidation. During the transfer of liquid steel from the ladle to the tundish, an inadequate slag carryover from the ladle increases the amount of slag in the tundish. This phenomenon can lead to excessive wear of the refractories of the tundish. Slag emulsification in the steel can also cause serious problems with non-metallic inclusions. To prevent these problems, it is usual to stop the teeming prematurely, leaving a considerable amount of steel in the ladle. This technique is not very satisfactory from an economic point of view. In the present investigation, vortex formation during the transfer of liquid steel from the ladle to the tundish was studied using physical modeling. A physical model of the ladle used at Belgo-Monlevade Steelworks was built in a 1:3 scale. In this model, water was used to simulate liquid steel and silicon oil for simulating slag. A DOE (Design Of Experiments) was implemented and the effects of the following factors and levels on vortex formation were analyzed: - Water flow rate coming out of the ladle (19 l/min or 28 l/min);- Waiting time the time interval between the complete filling and the start of the teeming of the ladle. (1 minute or 30 minutes); - Air bubbling through the bottom of ladle (with or without air injection); - Silicon oil use for simulating the slag (with or without oil); - Anti-vortex device (with or without this device). The response for each experiment combination was the water height (critical height) at the onset of vortex formation. Based on the results of the present investigation, some observations can be described. The ladle teeming physical simulation has shown that it was possible to identify the most important parameters for evaluating the vortex formation (critical height) and silicon oil and water emulsification. By comparing the simulation results of water with or without silicon oil, a significant difference was found for the critical height. Tests which were used silicon oil for simulating slag had obtained 12mm. Tests that were used only water had found 3mm. It is an important observation to highlight due to fact that simulations using only water and simulations using water and oil supernatant are not comparable. Besides, the results had indicated huge effects for water flow rate and the presence of anti-vortex device, considering the silicon oil use. By comparing waterflow rate on the same parameters, the critical height was 12mm for 19 l/min and 18mm for 28 l/min, which means the water flow rate modification led to a vortex formation higher than 51%. By analyzing the effectiveness of anti-vortex, the use of this device had reduced the critical height from 17mm for 12mm. Almost 41% according to level difference. That result had shown that a singular and simple device was effectiveenough to reduce the critical height.